Modern Node.js Development: When to Use CommonJS vs. ES Modules
Key Points on Node.js Modules: CommonJS vs. ES Modules
- CommonJS (CJS) is the traditional system: It uses
require()for imports andmodule.exportsfor exports, loads synchronously, and remains stable for legacy codebases, though it lacks modern features like top-level await. - ES Modules (ESM) represent the modern standard: They use
importandexport, support asynchronous loading, and enable advanced capabilities such as top-level await and static analysis for efficient bundling—making them future-proof and browser-compatible. - Choosing between them: Research suggests sticking with CommonJS for older projects or maximum compatibility, while ESM is increasingly preferred for new applications due to its alignment with JavaScript's ecosystem evolution.
- Interoperability is possible but nuanced: ESM can easily import from CommonJS, but the reverse requires dynamic imports, highlighting a gradual shift toward ESM in Node.js.
Overview of CommonJS
CommonJS has been Node.js's original module system, offering synchronous loading that's reliable for many existing packages. It's widely used but may feel less efficient in async-heavy scenarios.
Overview of ES Modules
ES Modules align with JavaScript standards, working seamlessly in browsers and Node.js. They introduce efficiencies like tree-shaking in bundlers, reducing bundle sizes, and simplify async code with top-level await.
When to Use Each
Evidence leans toward ESM for modern, scalable projects, especially those involving browsers or advanced tooling, while CommonJS ensures broad compatibility in established environments.
For more details, see the comprehensive explanation below.
Node.js has long supported modular code organization, allowing developers to break applications into reusable pieces. Two primary systems exist: the legacy CommonJS (CJS) and the standardized ECMAScript Modules (ESM). While CommonJS provides stability for older codebases, ESM offers modern features and cross-environment compatibility. This article explores their mechanics, differences, advanced capabilities, and best practices for use in Node.js applications.